That’s what Lauren Peterson, 33, thought, until two days later her urine had turned dark and her thigh muscles had become swollen and painful. Not exactly your standard DOMs.

"I was crying putting on my socks, my thighs hurt so bad," she told TODAY. “I was scared. I knew something was really wrong with me. I didn’t know what it was.”

When Peterson went to the emergency room, she found out that she had developed rhabdomyolysis, a potentially fatal condition where the skeletal muscle rapidly deteriorates.

It’s caused by either internal or external injury, and can result in kidney failure. "When the muscles break down, they release proteins that can potentially hurt the kidneys," Dr Maureen Brogan, the lead author of a report detailing Peterson's case, told TODAY.

So can spinning really cause this condition?

"Spinning is great exercise," says Dr Brogan. "But people should be aware they need to take it slow in the beginning. There should be some guidelines."

According to TODAY, the doctors had recently seen two other young adults who had similar symptoms after a spin class. The trouble with spinning is that "you’re using some of the largest muscles in the body — the quadriceps and the gluteus maximus — at an intense rate," says Dr Brogan.

If the exercise is too intense, she said, the muscles might not get enough oxygen, and can swell up, break down and even burst open.

Of course, that's not to say that you shouldn't keep spinning if you love it. Brogan recommends staying hydrated and being aware of the symptoms, such as extreme muscle soreness, nausea and vomiting, thigh pain and weakness, dark urine, and muscle swelling and tenderness.

The message? You can still love your spin class, just don't be a gym class hero - and make sure you listen to your body.